Engineering Fundamentals of the Internal Combustion Engine . I Willard W. Pulkrabek University of Wisconsin-· .. Platteville vi Contents 2-3 Mean Effective Pressure, 49 2-4 Torque and Power, 50 2-5 Dynamometers, 53 2-6 Air-Fuel Ratio and Fuel-Air Ratio, 55 2-7 Specific Fuel Consumption, 56 2-8 Engine Efficiencies, 59 2-9 Volumetric Efficiency, 60 , 2-10 Emissions, 62 2-11 Noise Abatement, 62 2-12 Conclusions-Working Equations, 63 Problems, 65 Design Problems, 67 3 ENGINE CYCLES 68 3-1 Air-Standard Cycles, 68 3-2 Otto Cycle, 72 3-3 Real Air-Fuel Engine Cycles, 81 3-4 SI Engine Cycle at Part Throttle, 83 3-5 Exhaust Process, 86 3-6 Diesel Cycle, 91 3-7 Dual Cycle, 94 3-8 Comparison of Otto, Diesel, and Dual Cycles, 97 3-9 Miller Cycle, 103 3-10 Comparison of Miller Cycle and Otto Cycle, 108 3-11 Two-Stroke Cycles, 109 3-12 Stirling Cycle, 111 3-13 Lenoir Cycle, 113 3-14 Summary, 115 Problems, 116 Design Problems, 120 4 THERMOCHEMISTRY AND FUELS 121 4-1 Thermochemistry, 121 4-2 Hydrocarbon Fuels-Gasoline, 131 4-3 Some Common Hydrocarbon Components, 134 4-4 Self-Ignition and Octane Number, 139 4-5 Diesel Fuel, 148 4-6 Alternate Fuels, 150 4-7 Conclusions, 162 Problems, 162 Design Problems, 165 Contents vii 5 AIR AND FUEL INDUCTION 166 5-1 Intake Manifold, 166 5-2 Volumetric Efficiency of SI Engines, 168 5-3 Intake Valves, 173 5-4 Fuel Injectors, 178 5-5 Carburetors, 181 5-6 Supercharging and Turbocharging, 190 5-7 Stratified Charge Engines and Dual Fuel Engines, 195 5-8 Intake for Two-Stroke Cycle Engines, 196 5-9 Intake for CI Engines, 199 5-10 Conclusions, 201 Problems, 202 Design Problems, 204 6 FLUID MOTION WITHIN COMBUSTION CHAMBER 206 6-1 Turbulence, 206 6-2 Swirl, 208 6-3 Squish and Tumble, 213 6-4 Divided Combustion Chambers, 214 6-5 Crevice Flow and Blowby, 215 6-6 Mathematical Models and Computer Simulation, 219 6-7 Internal Combustion Engine Simulation Program, 221 6-8 Conclusions, 225 Problems, 226 Design Problems, 228 7 COMBUSTION 229 7-1 Combustion in SI Engines, 229 7-2 Combustion in Divided Chamber Engines and Stratified Charge Engines, 243 7-3 Engine o?Itrating Characteristics, 246 7-4 Modern Fast Burn Combustion Chambers, 248 7-5 Combustion in CI Engines, 251 7-6 Summary, 259 Problems, 260 Design Problems, 261 Contents viii 8 EXHAUST FLOW 262 8-1 Blowdown, 262 8-2 Exhaust Stroke, 265 8-3 Exhaust Valves, 268 8-4 Exhaust Temperature, 269 8-5 Exhaust Manifold, 270 8-6 Turbochargers, 272 8-7 Exhaust Gas Recycle-EGR, 273 8-8 Tailpipe and Muffler, 273 8-9 Two-Stroke Cycle Engines, 274 8-10 Summary and Conclusions, 274 Problems, 275 Design Problems, 276 9 EMISSIONS AND AIR POLLUTION 277 9-1 Air Pollution, 277 9-2 Hydrocarbons (He), 278 9-3 Carbon Monoxide (CO), 285 9-4 Oxides of Nitrogen (NOx), 285 9-5 Particulates, 287 9-6 Other Emissions, 290 9-7 Aftertreatment, 292 9-8 Catalytic Converters, 293 9-9 CI Engines, 301 9-10 Chemical Methods to Reduce Emissions, 303 9-11 Exhaust Gas Recycle-EGR, 304 9-12 Non-Exhaust Emissions, 307 Problems, 308 Design Problems, 311 10 HEAT TRANSFER IN ENGINES 312 10-1 Energy Distribution, 313 10-2 Engine Temperatures, 314 10-3 Heat Transfer in Intake System, 317 10-4 Heat Transfer in Combustion Chambers, 318 10-5 Heat Transfer in Exhaust System, 324 10-6 Effect of Engine Operating Variables on Heat Transfer, 327 10-7 Air Cooled Engines, 334 10-8 Liquid Cooled Engines, 335 ~~~ ~ 10-9 Oil as a Coolant, 340 10-10 Adiabatic Engines, 341 10-11 Some Modern Trends in Engine Cooling, 342 10-12 Thermal Storage, 343 10-13 Summary, 345 Problems, 345 Design Problems, 348 11 FRICTIONAND LUBRICATION 349 11-1 Mechanical Friction and Lubrication, 349 11-2 Engine Friction, 351 11-3 Forces on Piston, 360 11-4 Engine Lubrication Systems, 364 11-5 Two-Stroke Cycle Engines, 366 11-6 Lubricating Oil, 367 11-7 Oil Filters, 373 11-8 Summary and Conclusions, 375 Problems, 376 Design Problems, 377 APPENDIX 378 A-I Thermodynamic Properties of Air, 379 A-2 Properties of Fuels, 380 A-3 Chemical Equilibrium Constants, 381 A-4 Conversion Factors for Engine Parameters, 382 REFERENCES 384 ANSWERS TO SELECTEDREVIEW PROBLEMS 392 INDEX 395 This book was written to be used as an applied thermoscience textbook in a one- semester, college-level, undergraduate engineering course on internal combustion engines. It provides the material needed for a basic understanding of the operation of internal combustion engines. Students are assumed to have knowledge of funda- mental thermodynamics, heat transfer, and fluid mechanics as a prerequisite to get maximum benefit from the text. This book can also be used for self-study and/or as a reference book in the field of engines. Contents include the fundamentals of most types of internal combustion engines, with a major emphasis on reciprocating engines. Both spark ignition and compression ignition engines are covered, as are those operating on four-stroke and two-stroke cycles, and ranging in size from small model airplane engines to the largest stationary engines. Rocket engines and jet engines are not included. Because of the large number of engines that are used in automobiles and other vehicles, a major emphasis is placed on these. The book is divided into eleven chapters. Chapters 1 and 2 give an introduc- tion, terminology, definitions, and basic operating characteristics. This is followed in Chapter 3 with a detailed analysis of basic engine cycles. Chapter 4 reviews fun- damental thermochemistry as applied to engine operation and engine fuels. Chapters 5 through 9 follow the air-fuel charge as it passes sequentially through an engine, including intake, motion within a cylinder, combustion, exhaust, and emis- xi xii Preface sions. Engine heat transfer, friction, and lubrication are covered in Chapters 10 and 11. Each chapter includes solved example problems and historical notes followed by a set of unsolved review problems. Also included at the end of each chapter are open-ended problems that require limited design application. This is in keeping with the modern engineering education trend of emphasizing design. These design prob- lems can be used as a minor weekly exercise or as a major group project. Included in the Appendix is a table of solutions to selected review problems. Fueled by intensive commercial competition and stricter government regula- tions on emissions and safety, the field of engine technology is forever changing. It is difficult to stay knowledgeable of all advancements in engine design, materials, con- trols, and fuel development that are experienced at an ever-increasing rate. As the outline for this text evolved over the past few years, continuous changes were required as new developments occurred. Those advancements, which are covered in this book, include Miller cycle, lean burn engines, two-stroke cycle automobile engines, variable valve timing, and thermal storage. Advancements and technologi- cal changes will continue to occur, and periodic updating of this text will be required. Information in this book represents an accumulation of general material col- lected by the author over a period of years while teaching courses and working in research and development in the field of internal combustion engines at the Mechanical Engineering Department of the University of Wisconsin-Platteville. During this time, information has been collected from many sources: conferences, newspapers, personal communication, books, technical periodicals, research, prod- uct literature, television, etc. This information became the basis for the outline and notes used in the teaching of a class about internal combustion engines. These class notes, in turn, have evolved into the general outline for this textbook. A list of ref- erences from the technical literature from which specific information for this book was taken is included in the Appendix in the back of the book. This list will be referred to at various points throughout the text. A reference number in brackets will refer to that numbered reference in the Appendix list. Several references were of special importance in the development of these notes and are suggested for additional reading and more in-depth study. For keeping up with information about the latest research and development in automobile and internal combustion engine technology at about the right technical level, publica- tions by SAE (Society of Automotive Engineers) are highly recommended; Reference [11] is particularly appropriate for this. For general information about most engine subjects, [40,58,100,116] are recommended. On certain subjects, some of these go into much greater depth than what is manageable in a one-semester course. Some of the information is slightly out of date but, overall, these are very informative references. For historical information about engines and automobiles in general, [29, 45, 97, 102] are suggested. General data, formulas, and principles of engineering thermodynamics and heat transfer are used at various places through- out this text. Most undergraduate textbooks on these subjects would supply the needed information. References [63] and [90] were used by the author. Preface xiii Keeping with the trend of the world, SI units are used throughout the book, often supplemented with English units. Most research and development of engines is done using SI units, and this is found in the technical literature. However, in the non-technical consumer market, English units are still common, especially with automobiles. Horsepower, miles per gallon, and cubic inch displacement are some of the English terminology still used. Some example problems and some review prob- lems are done with English units.